Answer:
The time taken to stop the box equals 1.33 seconds.
Explanation:
Since frictional force always acts opposite to the motion of the box we can find the acceleration that the force produces using newton's second law of motion as shown below:

Given mass of box = 5.0 kg
Frictional force = 30 N
thus

Now to find the time that the box requires to stop can be calculated by first equation of kinematics
The box will stop when it's final velocity becomes zero

Here acceleration is taken as negative since it opposes the motion of the box since frictional force always opposes motion.
Answer:
B train!
Explanation:
A train travelled at 40 km/hr. (120/3)
B train traveled at 45 km/hr (180/4)
True
False
False.
True
True
False
Answer:
-17.5 nC
Explanation:
charge A = -30 nC
charge B = -5 nC
After adding them it would be the average of the two charges because of the getting same voltage difference. so
c = (-30+(-5)) / 2 nC
c= -17.5 nC
answer is -17.5 nC
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